The problem is that a sovereign default increases the cost of capital for pretty much everyone in a nation. This generally results in a decrease in lending, and kills any markets that are dependent on lending (housing being a big one).
Basically, once the bankers have inflated financial bubbles everywhere, the impending crash is bad for the common man, UNLESS you're one of the lucky individuals that somehow became cash rich during the bubble, and can use the cash to buy up while the market/lending falls to pieces. Funnily enough, the cash rich ones seem to be the bankers, who, laden with bonuses from the bubble days, buy up property which they can rent to plebs to get a comfortable 6-10% pa return.
A great system, isn't it?!